7 Claims. (Cl. 229-35) This invention relates to non--skid or anti-slipping compositions for application to container materials, par-- ticularly cellulosic paper materials, including kraft bag stock, paperboard and the like. It also relates to cellulosic containers and container materials of the above paper type having outer surfaces coated with said compositions. This application is a continuation-in-part of my application Serial No. 552,961, filed December 13, 1955.

While the novel compositions of the present invention are suitable for treating a wide variety of paper container materials to enhance the surface frictioning qualities thereof, for reasons of simplicity the following description and discussion of prior art is directed to its use in connection with kraft paper bag material. In describing the container material product of improved slip resistance,

reference is also made to kraft paper. It is to be understood, however, that the present invention is not so limit+ ed, but is applicable to similar paper materials such as paperboard, etc.

In the accompanying drawing, Fig. 1 is a perspective partly in section of a multiwalled cellulosic packaging container bearing printed matter, the outer wall of which is coated with discrete particles of the anti-skid composition of the present invention. Fig. 2-is an enlarged end view of a similar bag with a section thereof cut away to illustrate multiwalled construction, and with the exterior surface of the outer wall coated with the anti-skid composition of the present invention.

Perhapsthe simplest approach to the manufacture of a paper which has more than average resistance to slipping upon itself is the formulation of a rough finish paper. For many applications, however, such a rough finish paper is not entirely satisfactory. For example, in the case of large multiwall bag containers, the surface of the rough finish paper was not sufi'iciently slip resistant to prevent toppling of bags piled upon themselves in transit as well as in storage. Obviously, the lower the density of the contents of such a large bag, the greater the likelihood of skidding and slipping when the bags are stacked. Although rough paper may be satisfactory in some instances, its surface has very poor printing characteristics, e. g., the rougher the finish, the more blotting or irregular spreading upon application of the ink, which results in printed matter unpleasant to the eye. Development of special inks to solve the spreading problem has met with only limited success.

the use of non-skid inks, but printing characteristics are not much improved.

Because of its lack of resistance to slipping, smooth kraft paper, although presenting an excellent surface for the acceptance of printing ink, is not ideally suited for multiwall bags. Recently, treatment of smooth kraft paper with dilute aqueous colloidal silica in the form of a sol has resulted in a measurable improvement in its slip resistance. If the paper is printed, the aqueous colloidal silica is generally applied following drying of the The frictioning qualities of the rough finish paper have been still further improved by 2,872,094 Patented Feb. 3, i959 printing ink. Treatment with an aqueous sol containing 3% by weight or less colloidal silica is not satisfactory, since the slip resistance of the finished bag tube is not superior to that of rough paper printed with nonskid ink. At concentrations of 6% by weight silica in the aqueous sol, a paper having an acceptable non-skid surface is possible, but at the expense of considerable sticking in the paper rolls, and in the case of multiwall bag stock, the interior tubes have been found to stick together in the tubing machine. This sticking is due to penetration of the treated layer of paper by the aqueous silica sol. Application at concentrations above 6% by weight silica in the treating sol, caused opposed similarly treated surfaces of kraft paper to turn white when rubbed together. Furthermore, at concentrations above 6% by weight the silica has an adverse effect upon the ink, changing the color thereof, for example, green ink is turned yellow. At these higher silica concentrations sticking is considerably more pronounced.

The use of sodium silicate solutions results in undesirable penetration of the paper with resulting sticking, without appreciably improving the surface frictioning qualities. In fact, solutions of sodium silicate are not as effective in the latter respect as sols containing about 6% colloidal silica, and sticking is more pronounced.

In view of the foregoing limitations upon the use of colloidal silica and particularly its property of penetrating the layer of paper treated rather than depositing silica only upon the surface, compositions containing colloidal silica alone leave a great deal to be desired in the preparation of a paper of improved resistance to slipping. The present invention provides novel coating compositions which overcome the above difliculties, permit deposition More specifically, there are now provided novel compositions containing colloidal silica as an active ingredient capable of imparting skid resistance to the surface of paper superior to that produced by the application of a composition containing colloidal silica alone. Smooth kraft paper surfaces treated with the present compositions are also more resistant to slipping than rough finish paper printed with non-skid ink. The novel coating compositions contain as essential ingredients a continuous phase, which is preferably water, and disperse solids in the weight ratio of about 3 to 16 parts of water to one part of solids. The solids comprise colloidal silica and a material hereinafter designated as an extender, with the silica and extender each present in amounts between about 3 and 15% by weight of the composition. The extender is a very finely divided material or powder which is chemically inert with respect to silica and the container material to be treated. It comprises clay (hydrated aluminum silicates) talc, diatomite, insoluble carbonates, insoluble magnesium salts and any of the naturally occurring materials employed as fillers or extenders in the printing ink and pigment arts, as well as mixtures thereof. Because of their abundance and ready availability, clays will usually be employed.

' The extender acts as a vehicle for carrying the silica particles to the sheet or material treated, while also preventing any objectionable penetration by the silica of the paper being treated, whereby the silica and extender are very largely retained on the surface. Furthermore, the presence of the extender provides a composition especially well suited for roller application to the finished paper or container stock. It has been found that a constant flow of the novel composition can now be maintained regardless of machine speed when applied by the roller, thus assuring a uniform coating on the paper. With colloidal silica alone, great difiiculty is encountered in maintaining a uniform flow in roller application. While the present compositions may also be applied by spraying either to unshaped container material or to the finished container as a paperboard box or bag, the resulting coatirig will generally be found to be less uniform. In' addi tion, necessary screening precautions may be required to eliminate occupational hazards frombreathing air containing a high percentage of colloidal silica particles and finely divided extender. Following application of the novel composition the treated surface is suitably dried or Container material surface-treated with the compositions of the present invention not only possess surface frictioning or anti-slip properties superior to treated materials heretofore available, but also the colloidal silica and extender deposited upon the surface of the material enhence its resistance to soiling, provide a surface of improved printing characteristics, add luster to the paper and to the ink, and afford a substantial measure of 'resistance to ink rub.

allowed to dry before the material is rolled or otherwise 111 Order establish improved p Iesistahce, tests contacted with it lf were conducted on unprinted and printed smooth finish When the composition is applied to a web by a roller, kl'aft P P The angle p Was similarly h 'h i the web running at h usual speed of a b as in each instance by measuring the angle of inclination at fed into a bag tubing machine, the roller, traveling at a Which uniformly loaded Sheets of P p Started to Shde circumferential speed equal to that of the travel of the p themselves- The angle was determmed for pp paper, can be made to pick up from a. pan sufiicient of unprinted, Pflhted t0 unprinted and PP f Pfmted t0 the material and apply it to the web in Contact thereprinted sheets before and after treatment with the comwith whereby the desired amount per i area ill he position of the present invention. The tests were carried distributed over the sheet. Furthermore, with the pres- P employing a f g chmPosltloh havlhg the follow ent compositions, the unexpected result is obtained that analysis y Welght? the coating applied to a'printed web adds substantially to P t the luster of the printed areas, and despite the presence Water 89 of the clayor the equivalent, the legibility of the printing S10 6 is in no way interfered with. Furthermore, the clay is Cl 5 adequately retained in place so that even when two sheets bearing the coating are rubbed firmly together, there is The paper sheets were coated uniformly and the coated no chalking or whitening, such as would indicate resurface allowed to dry. moval of the silica and clay from the paper. The following table shows the improvement in re- The novel compositions of the present invention are sistance to slipping of the treated paper:

preferably prepared by diluting to the desired degree a The novel compositions containingpcolloidal silica and colloidal solution of. hydrated silica or a polymerized the extender material, which is preferably very finely form of silicic acid, which does not contain any significant divided clay, as indicated above, may be applied to quantity of free alkali. In this latter respect at least the printed or unprinted paper either by spraying or by starting silica material is to be distinguished from alkali means of a roller. However, for high speed roller apmetal silicates for example, which are not employed. The plications to a heavily printed kraft paper web as the silica is usually in the form of an aquasol, or an organosame is fed into a bag tubing machine modification of aquasol. An aqueous product particularly well suited the coating compositions is desirable. Due to their nato the preparation of the compositions of the present inture, most inks resist wetting by water with the result vention is Ludox manufactured by the E. I. Du Pont that the aqueous composition is disposed at random in de Nemours, & Company containing about 30% by small droplets on the inked. surface, and deposition of weight colloidal silica, and having an Na O content besilica and extender is thus restricted to the areas covered tween about 0.09 and 0.11%.. Syton, the aqueous by these drops. In order to increase the slip resistance of colloidal silica of approximately the same concentration the paper surface, it is essential that a coating of silica manufactured by Monsanto Chemical Company may also and extender material be deposited substantially uniformbe employed. Following dilution of the sol with water, ly on the surface, whether the same be inked or not. the finely divided extender material .is dispersed with agi- Accordingly, it is Within the Scope of the Present invention tation throughout the resulting sol, thus forming the antito reduce the surface tension of the composition in order slipping composition. As indicated above, the solids in at he ink d r s may b r d nif rmly. Thi the treating composition, amounting to about 6 to 30% is accomplished by means of a wetting agent. of its weight, comprise about 3l5% by weight collodial Extensive tests indicated that a wide variety of inks, silica and about 315 by weight finely divided exincluding those having a very oily base, were most tender. The exact ratio of water to solids in the final easily and quickly wetted when the coating composition composition, as well as the proportions of silica and ex- Contained Small q n i f IIOII-iOIIiC Wetting ag tender in the solids is determined by the surface charac- Particularly the Complex Polyalkylene ellhel Wetting teristics, thickness and the type of paper or other conagehts- These Compounds are in general P p by tainer material which is to be treated. In the case of reacting a Water-insoluble hydrocarbon having one or smooth k f paper, the fo mula which produces the more reactive hydrogens with an alkylene oxide, for lowest acceptable increase in slip resistance is: water example, ethylene Oxide, as Set forth below, about 92%, colloidal silica about 3% and extender mate- RH" mnCEh-CH; --t 12 [onr-oHlo1mHm rial (clay) about 5%. For optimum improvement in slip resistance of this paper, compositions containing about 7 0 j to water, about 6 to 9% colloidal silica, and where n is the number of reactive bydrogens of com about 4 to 6% clay have been found quite satisfactory. 75

pound R and m is the number of alkylene oxide groups required to react with n number of hydrogens. The Wetting agents which are preferred are the complex nonionic polyethylene ethers, or polyethenoxy compounds, present in amounts between about 0.25 and 2% by weight of the total composition. A particularly eifective wetting agent of this type is Neowet which is manufactured by Royce Chemical Company, Carlton Hill, New Jersey.

While incorporation of a wetting agent of the above type permitted rapid wetting of the inked surface and resulting deposition of silica and extender uniformly on the ink surface, a great deal of foaming was encountered when the tuber was run at its normal high speed for prolonged periods. High roller speeds produced considerable agitation of the composition, causing it to foam and run over the sides of the press, even when only a very small quantity of wetting agent was employed. In order to counteract this undesirable characteristic of the wetting agent, the present invention contemplates the addition of a foam suppresser or defoaming agent to the coating compositions. Materials particularly well suited to this application are the silicones, and more particularly the less viscous, e. g., about 1 to 1500 centistokes, fluid dimethyl polysiloxanes having the generic formula These materials are highly efiective in eliminating foaming when present in the wetting agent-containing compositions in very low concentration, for example, between about 1 and 100 parts per million. Because of the dimculty of adding such small amounts, the polysiloxanes are often present in excess of 100 parts per million. The excess does not appear to be detrimental. Since the dimethyl polysiloxanes are immiscible with water, an emulsifier is necessary when they are employed in the present aqueous compositions. Suitable dimethylpolysiloxanes are available commercially as concentrated aqueous emulsions, and DoW-Cornings Antifoam AF has proved very successful when added to the compositions of the present invention. The latter material consists of about 30% by Weight dimethyl polysiloxane, about 12 to 14% of an emulsifier (glyceryl monostearate and a polyoxyethylene monostearate), with the balance of the composition being water.

The wetting agent and the foam suppresser are added to the aqueous colloidal silica-extender composition in such small quantities that the Water content of the compositions aforementioned for optimum improvement in slip resistance is not altered appreciably. A preferred composition, in percentages by weight, for high speed roller application, without foaming, to kraft bag stock having a large printed area on its surface is as follows:

The above formulation may of course also be applied to weight percent extender based upon the weight of the paper treated. However, it is difficult to speculate upon the weight percent solids which will be deposited upon lighter or heavier container material. It is safe to say that the silica and extender are uniformly disposed upon the surface treated in a weight ratio very nearly equivalent to their ratio in the aqueous treating compositions.

2. A composition as set forth in claim 1, wherein the finely divided extender material is selected from the group consisting of clays, talc, diatomite, insoluble carbonates, insoluble magnesium salts and mixtures thereof. 3. A composition as set forth in claim 2, wherein said wetting agent is a polyethylene ether and is present in amounts between about 0.25 and 2% by weight of the composition.

4. A composition for application to the printed surface of a kraft paper for imparting slip resistance thereto consisting essentially of about 3 to 15% colloidal silica, about 3 to 15% finely divided clay, about 0.25 to 2% of a non-ionic polythylene ether wetting agent, at least 1 to parts per million of an emulsified dimethyl polysiloxane foam suppresser, and the balance substantially water.

5. A smooth finished kraft paper bearing printed matter upon which there has been applied an aqueous composition consisting essentially of about 3 to 15% by weight colloidal silica, about 3 to 15% by Weight of finely divided extender material selected from the group consisting of clays, talc, diatomite, insoluble carbonates, in soluble magnesium salts and mixtures thereof, a nonionic polyalkylene ether wetting agent, an emulsified di-. methyl polysiloxane foam suppresser, and the balance substantially water.

6. A composition for application to the surface of cellulosic container material for imparting slip resistance thereto consisting essentially of about 3 to 15% colloidal silica, about 3 to 15% finely divided clay, about 0.25 to 2% by weight of a non-ionic wetting agent, at least 1 to 100 parts per million of a silicone foam suppresser, and the balance substantially water.

7. A cellulosic container material of improved slip resistance for use in the manufacture of cartons, single wall bags, the outer wall of multiwall bags, and the like upon which there has been applied a composition consisting essentially of about 3 to 15% by weight colloidal silica, about 3 to 15% by weight of finely divided clay, I

about 0.25 to 2% by weight of a non-ionic wetting agent, at least 1 to 100 parts per million of a silicone foam suppresser, and the balance water.